Validez del estudio

Cytokines are intercellular signaling peptides released from stimulated leukocytes, which induce the production of other cytokines and cell surface receptors through their effects on gene transcription (Cannon 2000, Grivennikov, Kuprash et al. 2006).

Chemokines are a family of chemotactic cytokines, which recruit monocytes, neutrophils, and lymphocytes to sites of injury and inflammation. Chemotaxis is induced through the activation of G-protein-coupled receptors, and the receptors that a given leukocyte expresses usually determines the chemokines to which it will respond (Charo and Taubman 2004). Chemokines are secreted by a variety of cell types, including leukocytes, fibroblasts, and endothelial cells (Roebuck, Carpenter et al. 1999).

While an increasing amount of literature exists to suggest that the initiation of the systemic inflammatory response plays a role in the myonecrosis associated with CS, no study to date has directly measured the cytokine/chemokine release induced by CS. A normothermic and normotensive model of CS was used in order to remove the possibility of a systemic inflammatory response secondary to hypoperfusion and shock.

Our study has confirmed that CS induces a systemic cytokine/chemokine release. Of the 24 cytokines/chemokines measured, 14 were detectable. Of the 14 detected, 12 were pro-inflammatory, 1 was anti-inflammatory, and 1 had both a pro- and an anti-inflammatory effect.

Six of the 14 cytokines/chemokines that were detectable were significantly elevated from their baseline levels after 2hrs of CS. These include TNF-α, IL-1β,

GRO/KC, MCP-1, MIP-1α, and IL-10.

TNF-α is a pro-inflammatory cytokine, and one of the first cytokines released with the initiation of inflammation. It serves as a chemoattractant for neutrophils, up- regulation of downstream cytokine/chemokine production, and it promotes the expression of adhesion molecules (Ascer, Gennaro et al. 1992, Yi and Ulich 1992, Seekamp, Warren et al. 1993, Krishnadasan, Naidu et al. 2003, Zhang, Hu et al. 2005).

IL-1β is a pro-inflammatory cytokine, and it is produced by activated macrophages. It is involved in multiple cellular functions including cell proliferation, differentiation, and apoptosis (Gao, Madi et al. 2014).

GRO/KC is a pro-inflammatory cytokine, and it is produced by macrophages and neutrophils. It serves to induce neutrophil chemotaxis. It is also seen in high levels in chronic inflammatory states such as chronic obstructive pulmonary disease (COPD) and rheumatoid arthritis (Bechara, Chai et al. 2007).

MCP-1 is a pro-inflammatory cytokine whose primary role is to recruit monocytes/macrophages to sites of injury (Shireman, Contreras-Shannon et al. 2007). MCP-1 is secreted by macrophages that have been induced by pro- inflammatory cytokines including TNF-α and IL-1β, and has been shown to play a role in angiogenesis following an ischemic stress (Lakshminarayanan, Lewallen et al. 2001). Additionally, MCP-1 exerts its effects by binding to leukocytes, and targeting them for activation (Yadav, Saini et al. 2010).

MIP-1α is a pro-inflammatory cytokine and is produced by macrophages, lymphocytes, and dendritic cells. It is chemotactic for cells of the monocyte lineage as well as for lymphocytes. Additionally it appears to inhibit the proliferation of hematopoietic stem cells (Cook 1996).

IL-10 is an anti-inflammatory cytokine, and is produced by monocytes, macrophages, dendritic cells, and lymphocytes. It is an inhibitor of antigen presentation, and prevents the differentiation of monocyte precursors, and the maturation of dendritic cells (Mosser and Zhang 2008).

The results of our study have confirmed that CS induces a substantial, and predominantly pro-inflammatory response. The initiation of the systemic inflammatory response should, therefore, be considered in the pathophysiology of CS. The systemic inflammatory response is complex and redundant therefore, the

exact mechanism of initiation and the interplay between cytokines and chemokines in CS needs to be further delineated.

To our knowledge, this is the first study that directly confirms CS as an inflammatory process. The results are the beginning step, in order to extrapolate the mechanisms by which injury occurs. The identification of specific mediators could potentially serve as pharmacologic targets in future studies in an attempt to decrease the devastating consequences of CS.

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